Electronic apparatus for timing events



Jan. 12, 1960 T. c. NUTTALL 2,921,253

ELECTRONIC APPARATUS FOR TIMING EVENTS Filed Oct. 19, 1956 s Sheets-Sheet 1 PULSE ssnsmoa a 2 I 3 DETECTOR a sm SELECTIVE eeusmoa AMPLIFIER T DETECTOR a MASTER PHASE OSCILLATOR CHANGER Jan. 12, 1960 T. c. NUTTALL 2,921,258

ELECTRONIC APPARATUS FOR TIMING EVENTS Filed Oct. 19, 1956 3 Sheets-Sheet 2 STEP J f GENERATOR 8-- MASTER PULSE at? W GENERATOR DETECTOR AMPLIFIER V 1 l SELETIVE H 7 P ASE J AMPLIFIER CHANGER CR1 [0 Mc/s DETECTOR AMPLIFIER BNNFREOUENCY IO 6 DIVIDER I S lMc/s l 3X I 7, I31 SELECTIVE Ki AMPLIFIER lMc/s r! Y I FREO,UENC 1O 6 8 DIVIDER I00 Hc/s II V 3 I I l3 SELECTIVE j AMPLIFIER I00 Mc/s Jan. 12, 1960 r. c. NUTTALL 2,921,258

ELECTRONIC APPARATUS FOR TIMING EVENTS Filed Oct. 19, 1956 3 Sheets-Sheet 3 1 2 :7 osracron I I STP 5 M/s FREQUENCY SELECTIVE csusmoa AMPLIFIER oouam 6 omcron IO file/s MASTER PHASE I OSCILLATOR ER T0 T0 PULSE GENE AMPLIFIERS 4 9, l0

ELECTRONIC APPARATUS FOR TIMING EVENTS Claims priority, application Great Britain October 19, 1955 7 Claims. (Cl. 324-68) England, assignor to London, England, a British This invention relates to improvements in electronic apparatus for timing events and has particular application when it is required to determine with very great accuracy the duration of the time interval or intervals between two or more successive events. The principle of using an electronic counter to count the number of cycles of a train of signals of constant periodicity which pass through a gate opened by the first event and closed by the second has been successfully employed for relatively low accuracies of measurement, say, down to a time resolution of one micro-second. The difliculties which arise when it is attempted to apply this principle to obtain a higher resolution are, however, formidable. Resolution to one-tenth microsecond would be feasible, though difficult, but an extension to one-hundredth microsecond appears to be quite impracticable by any development of counter techniques which can at present be envisaged. Difficulties arise both in the counter circuits themselves and in the gating circuits used for starting and stopping the train of signals, since these must operate without the risk of leaving a mutilated signal at the 7 beginning or end of the train, which might lead not merely to a unit error in the count but to the disabling of the counter and a resultant gross error.

The present invention provides an alternative approach I to the problem which avoids the above described difiiculties by eliminating the necessity for counting and gating circuits. The start-stop principle is not used; instead a continuously-running chronometer is provided and the individual events are arranged to cause an instantaneous record to be made of the condition of the chronometer so that the time-interval between them is obtained by subtraction of the respective recorded times.

One object of the invention is to provide a method of timing events in which the difiiculties above described are avoided by eliminating the necessity for counting and gating circuits, since the start-stop principle of operating need not be used.

Another object of the present invention is to provide a method of timing events in which a continuously-running chronometer is used and in which the occurrence of each event to be timed is caused to derive an instantaneous record of the condition of the chronometer at the time of the event.

A further object of the present invention is to provide apparatus for indicating the instant of occurrence of an event in relation to a timing oscillation.

A collateral object of the invention is to provide apparatus for indicating by means of a visual display the time of occurrence of an event in relation to a timing oscillation.

An extension of this aspect of the invention is to provide apparatus for obtaining a visual display in decimal fractions of a second of the time of occurrence of an event in relation to a timing oscillation.

In accordance with the invention, apparatus for indi- United States Patent -cating the instant of occurrence of an event in relation consisting of the smoothed *1 mc./s., 10 kc./s. etc.

' outputs in quadrature.

to a timing oscillation of predetermined frequency comprises means responsive to the occurrence of said event to yield an electric signal including an abrupt voltage step having a predetermined temporal relation to said occurrence. This voltage step signal is applied to a plurality of circuits having individual selective responses respectively equal to the frequency of said timing oscillation and submultiples thereof. The ringing frequency oscillatory voltages developed in these selective circuits have phases which are determined by the instant of occurrence of the event to be tuned. These ringing signals are then applied to individual ones of a plurality of display means equal in number tothe number of said plurality of selective circuits. Each of said display means is responsive to two applied signals to provide a visual indication determined by the phase difference between the applied signals. A plurality of control signals having individual frequencies equal to that of said timing oscillation and of submultiples thereof like to the. submultiples at which said selective circuits have responses are derived from the output of a master oscillator which generates the timing oscillation and are also applied individually to the display means fed with signals from respective selective circuits, so that each of said display means displays an indication of the phase relation between one of said ringing signals and a control signal of like frequency derived from said timing oscillation. Since the temporal relation between each ringing signal and the instant of occurrence of the event is predetermined the phase relations between each control signal and the corresponding ringing signal together may serve as an indication of the time of occurrence of the event.

Preferably each of the display means comprises two phase sensitive detector circuits, which may conveniently be balanced modulator circuits which yield output signals products of two applied sig nals. To each of these detector circuits is applied firstly the ringing signal derived from the selective circuit and secondly an oscillatory control voltage of like frequency derived from and locked in phase to the timing oscillation. The control voltages are mutually displaced in phase by so that the outputs from the two detector circuits will vary in amplitude according to the phase relation betweenthe ringing signal and the timing oscillation. These output signals are used to control the direction of defiection of the electron beam of a cathode ray tube which thus traces on its screen a line of which the inclination to a fiducial line is determined by the phase relation between the ringing and control signals and hence upon the instant of occurrence of ,the event to be timed.

In carrying out the present invention a convenient form of apparatus for timing an event in relation to a master chronometer providing a 10 mc./s. timing oscillation may be as follows:

The master chronometer comprises a crystal oscillator which by means of multipliers and/or dividers produces a number of output frequencies such as 10 mc./s., The waveforms are sinusoidal and each frequency is supplied in two-phase form, i.e. two The various frequencies are maintained in fixed phase relation to each other.

Each event to be timed is arranged by known means -to produce an electrical signal of step waveform. The

to the narrow band characteristic the shape of the envelope will be ill-defined but this is immaterial since the essential information is contained in the phase of the ring. I p p V The ringing signal is fed to tw'o balanced demodulators or phase sensitive detectors energised by the two quadrature components of the standard mc./ s. oscillator. The outputs of the two 'dernodulators are pulses of the same shape as theenvelope of the ring, the ratio of their amplitudes being equal to the tangent of the phase angle of the ring with respect to the standard 'oscil- 'lator.

v The pulses from the demodulators are fed through matched amplifiers to the vertical and horizontal deflection plates of a cathode ray oscilloscope tube. These amplifiers must preserve amplitude linearity. They need have only a restricted frequency range, so that the pulses 'are greatly prolonged, but the frequency characteristics must be matched so that the pulses die away with the same time constant. Thus the oscilloscope spot is de- 'flected off the screen and then returns more slowly to the centre. The matching of the amplifiers ensures that --the spot excursion is confined to a straight radial line.

The original signal is conveniently arranged to generate abrightening signal for the tube so that the spot is .illuminated during its return stroke from the outside to the centre of the screen, and is extinguished again as the spot settles down at the centre of the screen. Thus the spot draws a pointer of which the angle corre- 'sponds directly to the phase of the signal with respect to the master oscillator, and if the circumference of the cathode ray tube screen is marked off in ten equal parts numbered 0-9 the pointer will indicate time directly in 'hundredths of a microsecond.

f In the processing of the signal to produce the' oscilloscope deflections the band width is progressively reduced and the signal duration prolongedi The drawing of the pointer may therefore bearranged to occupy a time of at least a few' hundred microseconds, so that it becomes possible to produce adequate brightness either for photographic recording or even for direct observation if a long persistence phosphor is employed.

The features of this invention which are believed to -be novel are set forth with particularity in the appended claims. The invention itself, however, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings,'in the several figures of which like numerals are used to designate similar circuits or'devices and in which:

Figure 1 is a block schematic diagram of part of one embodiment of apparatus according to the present invention,

Figures 2, 3 and .4 are diagrams illustrating electric signals such as arise in the circuit of Figure 1,

Figure 5 is a partial schematic diagram illustrating one embodiment of apparatus according to the invention,

Figure 6 is a diagram illustrating the method of ob- "taining information as to the timing of an event by the use of apparatus as illustrated in Figure 5 and Figure 7 is a schematic diagram illustrating an alternativ'e embodiment of apparatus according to the invention.

Figure 1 shows a part of an embodiment of the invention. The diagram shows means forindicating the instant of occurrence ,of an event inrelation to a single timing oscillation having a frequency of 10 mc./s.

An event to be timed, represented by arrow 1 affects a step-generator device 2 and causes it to develop an electric signal including an abrupt voltage transition, such 'as that shown in Figure 2', at a time related in a prede- -termined manner to the instant of occurrence of the event and preferably substantially simultaneous therewith. It will be seen from Figure '2 that the generated transient has a 'very short rise-time, of the order of 0.2 as.

# The device 2 .for developing an electric. step signal of occurrence of the event to be timed may be of any known kind suitable to the nature of the event. For example, the passage of an object past a fixed point may be arranged to cause an electric circuit to be closed or opened, or may producea sudden changein the illumination of a light-sensitivedevice yielding a corresponding change in current in its associated circuit and hence a voltage change across a circuit impedance. In many applications the event may itself comprise a voltage step. Many such arrangements have been described and it is not thought necessary to particularize further by describing in detail any known arrangement.

The step function generated by device 2 is applied firstly to a selective amplifier 3 which comprises at least one oscillatory circuit of low decrement tuned to resonate at the frequency of the master oscillator which generates the timing oscillation, viz 1O rnc./s. The step function from device 2 is also applied to a pulse generator 4 of known type, conveniently a suitable one-shot multivibrator, which generates a pulse having an amplitude and duration appropriate to its purpose of brightening the display on the screen of a cathode ray tube as further described later in this specification.

The application of the step function from generator -2 to selective amplifier 3 causes the amplifier to produce an oscillatory voltage or ring having the natural frequency'of the tuned circuit and persisting for a large number of cycles as shown in Figure 3. This 10 mc./s. ringing signal is applied to one input terminal of each of two detector circuits 5, 6. These detector circuits are each best constructed as balanced demodulators which yieldoutput signals comprising the smoothed product of two applied input signals.

The demodulators also receive other input signals which are derived from a phase changer 7 fed by amaster oscillator 8 which generates a timing oscillation'of predetermined frequency. The outputs from phase changer 7 are both sinusoidal signals at the frequency of the master oscillator but they are mutually displaced in phase by 90.

The outputs from the two demodulators 5, -6 are pulses having the same form as the envelope of the shock excited oscillatory voltage developed in selective amplifier 3 and illustrated in Figure 3. The form of these pulses is therefore as shown in Figure 4. These pulses are fed through matched phase-splitting deflection amplifiers 9,

10 which supply deflection potentials to the horizontal pinge upon a fluorescent screen 18 applied to the inner surface of the end of tube 13.

-th am i de re ati n fi t in t Signals h ch ey receive that is, they are linear amplifiers. They need ha on y-a r t ed f eque cy range, s th t e pu are sre t yr ol s dt the r f q ncy sharas sristis a phase changer 7".

are matched so thatthe pulses die away with the same time-constant. The outputs from these amplifiers deflect the electron beam of tube 13 off the screen and then allow it to return slowly to the centre. The matching of the amplifiers ensures that the spot excursion is confined to a straight radial line.

The brightening pulse applied to modulator 16 is arranged to have a duration such as to allow the beam to be effective to excite the screen during its return stroke from the periphery to the centre of the screen but to extinguish the beam when it comes to rest at the screen centre. l

The beam thus draws a pointer of which the angle corresponds directly to the phase ofthe signal with respect to the raster oscillator signal. If the periphery of screen 18 of tube 13 be divided into ten equal sectors numbered -9 the pointer will indicate the phase difference between the oscillation from amplifier 3 and the master oscillation directly in hundredths of a microsecond.

In the processing of the signal to produce the oscilloscope deflection potentials the band width is progressively reduced andthe signal duration prolonged. The drawing of the pointer may therefore be arranged to occupy a time of at least a few hundred mTcroseconds, so that it becomes possible to produce adequate brightness either for photographic recording, or even for direct observation if a long persistance phosphor is employed.

The apparatus so far described has provided an indicator showing the time interval between an exciting signal and a master oscillation in hundredths of a microsecond. Where intervals greater than 0.09 microsecond are required to be indicated it is necessary to provide also indications of larger fractionsof a second. This is done in accordance with the present invention by adding additional circuits similar to that described in relation to Figure l but fed with oscillations of lower frequency derived by frequency subdivision from the master oscillator. Such an arrangement suitable for indicating time intervals up to 9.99 microseconds is illustrated in Figure 5.

In Figure 'an event symbolized by arrow 1 is caused to control a step generator 2. The output from generator 2 is in this case applied to three selective amplifiers 3, 3'

and 3" which have decimally related preferred frequencies. The preferred frequency of amplifier 3 is that of a master oscillator 8, which in the present example is mc./s. The preferred frequency of amplifier 3' is 1 mc./s.

output from each selective amplifier is applied to pairs of associated demodulator circuits 5, 6; 5', 6' and 5", 6" .respectively. Each pair of demodulator circuits is supplied from phase changing circuits 7, 7' and 7" respecand that of amplifier 3" is 100 kc./s. The oscillatory i tively with oscillatory voltages in quadrature and having the appropriate frequency. Phase changer 7 is controlled directly by the It) mc./s. signal from a 10 mc./s. master oscillator 8. Phase changer 7' is controlled by the output signal from a frequency dividing circuit 8' which divides by a factor of 10 the input frequency of 10 mc./s. applied to it from master oscillator 8 and thus yields a 1 mc./s. output signal. Phase changer 7" is similarly controlled by the output from a similar frequency dividing circuit 8" which is fed with a 1 mc./s. output from divider 8 and itself divides the frequency of the applied signal by a factor of 10 to yield a 100 kc./s. signal to The outputs from each pair of demodulators are applied torespective matched pairs of amplifiers 9, 10; 9', 10 and 9", 10" which each control the deflection of the' electron beam of associated cathode ray tubes, 13,

13', 13". The step wave generated by generator 2 is their traces at the appropriate times.

Each'cathode ray tube will operate as a dial indicating the timing of the event which caused the signal applied to terminal 1 in appropriate decimal fractions of a second. Tube 13 will indicate time in hundredths of a microsecond, tube 13' tenths of a microsecond and tube 13" microseconds.

The cathode ray oscilloscope tubes are conveniently mounted as illustrated in Figure 6, the screens of each of the three tubes 13, 13 and 13" being displayed through appropriate apertures 24, 25, 26 in a panel 27 upon which are marks dividing the circumference of each aperture into ten equal parts. Each set of divisions is numbered from 0 to 9 and the release of the electron beams of the oscilloscope tubes by the pulse from pulse generator 4 will produce on the screen of each tube a luminous line of which the position is determined by the timing of the event. In the drawing, these lines are shown as black lines 28, 29, 30.

The pointers 28, 29, 30 displayed on the cathode ray tubes 13, 13, 13" behave as do pointers connected by continuous rather than intermittent gearing and they must be read in the same way as gas meter dials. For example, in expressing a time such as 2.96 ,uS. the microseconds pointer 30 will point to 3 rather than 2, as is illustrated in Figure 6, and the correct interpretation is obtained from a consideration of the 0.96 s. which accounts for almost another microsecond; The indicators must therefore be read by starting with the least significant, each figure read then providing the clue for the next more significant figure.

In an alternative embodiment of the invention, also for timing an event in relation to a 10 mc./s. timing oscillation, the first circuit to which the step waveform produced by the event to be timed is applied is arranged to resonate at 5 mc./s. and the ringing signal developed across it is applied to a frequency doubling circuit including a circuit resonant at 10 mc./s. The signal arising across this latter circuit is then applied to phase-sensitive detectors as before.

Part of this alternative embodiment of the invention is illustrated in Figure 7, which shows that part of an apparatus which differs from the arrangement shown in Figure 1 and which also is suitable for timing an event in relation to a 10 mc./s. timing oscillation. As before the event 1 to be timed is applied to control a step Wave generator 2. The voltage step produced by generator 2 is applied toa selective amplifier 3 which in this case has a preferred frequency of 5 mc./s. The output signal from selective amplifier 3 is then applied to a frequency doubling circuit 31 which yields an output signal which is zero in the absence of an input signal but is of twice the frequency of the signal applied to its input, that is, 10 mc./s., when a 5 mc./s. signal is applied to it.

The frequency-doubled signal is applied as before to demodulators 5 and 6 to which are applied 10 mc./s. signals which are in quadrature to one another and are developed by a phase changer 8 driven by a 10 mc./s. master oscillator 7.

Owing to the fact that the output from the frequency changer 31 is zero in the absence of an input signal the effect of noise upon the system is reduced, as compared with the embodiments described in relation to Figures 1 and 5.

Although the embodiments above described have employed two demodulator circuits, this is not a necessary condition for applying the invention. Any advantageous larger number of demodulators may be employed, provided that each demodulator is fed with a control signal of the timing frequency and differing appropriately in phase from the signals applied to the other demodulators.

It is considered that a four-phase system may be found advantageous, since this is ,a balanced embodiment of the simplest two-phase arrangement, but where direct operation of a computer working with the decimal notation -to each of said display means.

sponsive to the occurrence of said event to generate an electric signal comprising .an abrupt-voltage step, a plural- ,ity of circuits having individual selective responses at ringing frequencies respectively equal to the frequency of said timing oscillation and submultiples thereof, means for applying said step signal equally to each of said circons to develop therein individual ringing signals at said ringing frequencies and of phases determined by the in stant of occurrence of said event, a plurality of display means equal in number to the number of said selective circuits and each responsive to two applied signals to provide a visual indication of the phase difference therebetween, means for generating said timing oscillation,

frequency divider means fed with .said timing oscillation to develop a plurality of control signals at the frequency of said timing oscillation and at submultiples thereof equal to said ringing frequencies and means for applying a ringing signal and a control signalof like frequency 2. Apparatus according to claim l'wherein the frequencies of said ringing signals and of .the corresponding control signals are decimal submultiples of the frequency of said timing oscillation.

3. Apparatus according to claim 1 in which the frequency of said timing oscillation is a decimal multiple of step signal to each of said selective circuits to develop therein oscillatory signals at the frequency of said timing oscillation and of said selected submultiples thereof and having phases determined by the instant of occurrence of said event a plurality of sets of detector circuits, each circuit having a first and a second input terminal and being each arranged to yield an output signal comprising the smoothed product of signals applied to said input terminals, means for applying one of said oscillatory signals of ringing frequency equally to said first input terminal of each of one set of said detector circuits,

--means for generating said timing oscillation, means fed yWllTh said timing oscillation for developing a plurality of sets of control signals equal in number to the number of sets of said detector circuits and of like frequencies equal to that of said timing oscillation and of said selected submultiples thereof but mutually displaced in phase, means for applying each signal of each of said sets of control signals to an individual one of the corresponding set of said detector circuits, a plurality of display devices each responsive to varying amplitudes of a plurality of applied signals for producing a visual indication of the amplitude relations between said signals, and means for applying the outputs from said detector circuits in sets to control 4 individual ones of said display devices.

5. Apparatus for indicating the instant ofoccurreme ringing frequency and said selcctedsubmul-tiples thereof,.

said signals having phases determined by the instant of occurrence of said event, a plurality of pairs of detector circuits each having a first and a second input terminal and being each arranged to yield an output signal includingthe smoothed product of signals applied tosaid input terminals, means for applying said oscillatory signals of ringing. frequency from each of said circuits equally to said first terminal of each of a pair of detector circuits, means for generating said timing oscillation, means fed with said timing oscillation for developing pairs of control signals of like frequencies equal to those of said timing oscillation and of said submultiples thereof, the signals of each pair being displaced in phase by 90", means for applying said pairs of control signals each to an individual one of said second input terminals of a pair of said detector circuits, a'plurality of cathode ray tubes each including a luminescent screen, means for developing an electron beam within each of said cathode ray tubes to produce visual indications upon each of said screens of the point of impact thereupon of one of said beams, means for deflecting each of said beams in two coordinate directions under the control of applied signals,

and means for applyingthe output signals from said detector circuits each to control the deflection of one of said electron beams in one said direction.

6. An apparatus according to claim 5 and comprising also pulse generator means for developing a pulse of predetermined duration in response to an applied signal, means for applying said step signals to said pulse generator means to cause the production of a pulse, biasing means for biasing a modulator electrode in each of said cathode ray tubestso causing the electron beam of each of said cathode ray tubes to be suppressed except when p a positive pulse is applied to said modulator electrodes and means for applying pulses developed by said pulse generator to said modulator electrodes to cause the production of said electron beams.

7. Apparatus for determining the instant of occurrence of an event in relation to a timing oscillation of predetermined frequency, comprising in combination: means responsive to the occurrence of saidevent to yield an electric signal including an abrupt voltage step having a predetermined temporal relation to said event, a circuit having a selective response at a ringing frequency equal to one-half that of said timing oscillation, a frequency doubling circuit to develop a ringing signal of frequency said selective circuit to develop therein an oscillatory signal at said ringing frequency and means vfor applying said signal of ringing frequency to said frequency doubling circuit, means for applying said step signal to equal to that of said timing oscillation, and of aphase determined by the instant of occurrence of said event, means for applying said step signal also to a plurality of circuits having selective responses at ringing frequencies equal to different submultiples of the frequency of said timing oscillations lower than the second to develop therein ringing signals at said submultiple frequencies and of phases determined by the instant of occurrence of said event, a plurality of display means equal in number to the number of said selective circuits and each responsive to two applied signals to provide a visual indication of the phase difference therebetween, means for I generating said timing oscillation,- frequency divider means fed with said timing oscillation to develop a plugot an. event-in relation to a timing oscillation of predc rality oi .controlsignals at the frequency of said timing oscillation and at submultiples thereof equal to said ringing frequencies, and means for applying a ringing signal and a control signal of like frequency to each of said display means.

References Cited in the file of this patent UNITED STATES PATENTS 2,432,196 Hershberger Dec. 9, 1947 Eastori June 29, 1948 Schlesinger June 19, 1956 FOREIGN PATENTS Great Britain Oct. 31, 1949 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,921,258 January 12, 1960 Thomas Cayton Nuttall It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the grant, lines 2 and 3, for "assignor to Cinema- Television Limited, of London, England, a British company," read assi gnor to Rank Cintel Limited, a British company, line 12, for "Cinema-Television Limited, its successors" read Rank Cintel Limited its successors in the heading to the printed specification, lines 3, 4, and 5, for "assignor to Cinema-Television Limited, London, England a British company" read assignor to Rank Cintel Limited, a British company Signed and sea led this 13th day of September 1960.

(SEAL) Attest:

KARL 1-1. AXLINE ROBERT c. WATSON Y Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTION Patent No. 2,921,258 January 12, 1960 Thomas Cayton Nuttall It is hereby certified that error appears in the alcove numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the grant, lines 2 and 3, for "ass'ignor to Cinema Television Limited, of London, England, a British company," read assi gnor to Rank Cintel Limited, a British company, line 12, for "Cinema-Television Limited, its successors" read Rank Cintel Limited its successors in the heading to the printed specification, lines 3, 4, and 5, for "assignor to Cinema-Television Limited, London, England, a British company" read assignor to Rank Cintel Limited, a British company Signed and sealed this 18th day of September 1960.

(SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents 

